Process for improving fats



July 8, 1969 P. J. SEIP PROCESS FOR IMPROVING FATS Sheet Filed May 11, 1964 July 8, 1969 P. .J. SEIP I 3,454,608

PROCESS FOR IMPROVING FATS V 4 Filed May 11, 1964 Sheet 2 0f 5 July 8, 1969 P. J. SEIP PROCESS FOR IMPROVING FATS Sheet Fild May 11, 1964 P. J. SEIP PROCESS FOR IMPROVING FATS July 8, 1969 Sheet Filed May 11, 1964 ML "511E y 1969 P. J. SEIP 3,454,608

PROCESS FOR IMPROVING FATS Filed May 11, 1964 Sheet 5 of s United States Patent 3,454,608 PROCESS FOR IMPROVING FATS Paulus Johannes Seip, Zwijndrecht, Netherlands, assignor to Lever Brothers Company, New York, N.Y., a corporation of Maine Filed May 11, 1964, Ser. No. 366,240 Claims priority, application Great Britain, May 14, 1963, 19,008/ 63 Int. Cl. Cllb 3/06 US. Cl. 260425 8 Claims ABSTRACT OF THE DISCLOSURE The invention concerns a continuous process for refining glyceride oils by treatment with alkali in which the oil flows smoothly through a series of stages in the 'form of an upper layer on an aqueous solution of the alkali, the composite stream being transferred between successive stages in such a way that the soap layer formed by reaction of the alkali with the free fatty acid in the oil is dispersed into the body of the aqueous phase, thus exposing a fresh aqueous surface at the interface enabling the neutralization reaction to proceed. Apparatus is described including guide members causing a change in direction in the flow of the composite stream or by separating the layers between successive stages through which they flow.

This invention relates to a process and apparatus for the alkali refining of glyceride oils.

In this specification the term glyceride oils is used to include fatty acid glycerides which are normally solid as well as those which are normally liquid.

Glyceride oils obtained by extraction or pressing or other methods from vegetable or animal raw material always contain a greater or smaller amount of free fatty acids. Before these oils can be used in the preparation of foodstuffs, the free fatty acids and other impurities must be substantially removed. The oldest and best-known deacidification process is alkali-refining. This process has the advantage that at the same time a purification of the oils is brought about by absorption in the soap formed of a number of the undesirable substances present in the crude oil. This purifying effect obtained in alkali-refining has a great influence on the results obtained in subsequent processes such as bleaching, hardening and deodorising. In deacidification methods inwhich caustic soda solutions are used, however, it is difficult to prevent saponification of glycerides. Moreover, one always finds neutral oil in the soap solution. This leads to the presence of neutral oil in the acid oil which is obtained when the soap is split by acid hydrolysis and to reduction in the yield of refined oil. In general acid oils containing 30-40% or more of neutral oil are still quite usual. It is possible to recover neutral oil of a fair quality from the soap solution, but this is rather expensive and therefore industrially unsatisfactory. In the literature several methods have been proposed to reduce the losses inherent in alkali-refining. It has, for example been proposed to .used dilute caustic soda in neutralisation, but this increases the tendency of the soap solution to form emulsions. Further, it has been proposed to use less alkaline compounds, such as soda ash and ammonia, and to deacidify with the help of centrifuges, using very short contact times between oil and the alkaline solution. Although these proposed methods give some improvement, the oil losses still remain considerable.

In general de-acidification may be regarded as a liquidliquid extraction process, but there are certain features that make this process complicated. The fatty acids are not extracted with the aid of a selective solvent, but are ice taken up into the alkaline solution while forming soap. However, in addition to this desirable action of the alkaline solution, undesirable side reactions may occur. An example of such side-reactions is saponification of the oil by the alkaline solution. Further, the refining process is strongly effected by what happens at the oil-lye interface.

According to a recent proposal, oil droplets of substantially uniform size are introduced without turbulence into an excess of lye. Although in this way the usual refining losses may be reduced, various disadvantages are involved. Thus it is very difiicult to make droplets of the same size, and this requirement is very stringent since smaller droplets will rise in the lye at a lower velocity than larger ones and owing to their small size they are de-acidified more rapidly. As soon as the fatty acid is removed, the rate of saponification increases. Moreover, it is very difficult to avoid turbulence completely. These factors result in an increase in the saponification loss. Decreasing the path length causes the free fatty acid content of the neutralised oil to rise, since larger droplets may escape complete neutralisation. Turbulence may prevent droplets even of the same size having the same residence time in the lye, and results in some of them undergoing excessive saponification. This reduces their size and makes them even more sensitive to turbulence. Moreover the lye concentration decreases during the neutralisation, so that a longer path for the droplets is required to ensure complete neutralisation by the end of the process. Also some particular oils can give rise to difficulties owing to unsatisfactory coalescence of the droplets at the top of the column.

Neutralisation can also be effected by contacting the oil in the form of a thin layer with the lye but grave difficulties have been encountered in devising a satisfactory metohd of neutralising the oil in this form. Thus, we have found that if the oil is caused by means of an inclined plate to flow slowly upwards through a stationery body of lye, the rate of neutralisation decreases progressively along the path of the layer and soon becomes zero so that in the product the desired low free fatty acid content is not obtained. We found also that causing the lye to flow either with the oil layer or counter thereto does not avoid the defect. Similar results are obtained if, instead of an inclined straight guide plate a series of such guide plates arranged in a zig-zag, or helical guide plate are used.

In the course of extensive research carried out with a view to devising a satisfactory method of neutralising the oil in the form of a thin moving layer we found that the defects referred to above are bound up with the growth, along the path of the oil layer, of a layer of aqueous soap solution separating the oil layer from the lye. The problem then arose of removing the soap layer without causing undue emulsification of the oil in the lye, or of lye in the oil or excessive saponification or excessive use of lye or undue complexity in the system.

We have now found that satisfactory results are obtained where the oil is contacted with an aqueous alkaline solution in a plurality of separate stages, in each of which the oil flows as a thin coherent layer on the surface of a moving stream of aqueous alkaline solution along a path in which any inclination to the horizontal is upwards at a small angle, and between consecutive stages any layer of aqueous soap solution that has been formed is removed from contact with the oil layer, the oil then being passed to the next stage and the alkaline solution to a following or preceding stage, substantial intermixture of the oil with alkaline solution or aqueous soap solution being avoided throughout.

Preferably in each stage the oil layer moves slowly upwards in the same or the opposite direction to the alkaline solution as a result of its lower specific gravity and at intervals the oil is caused to change the direction of its flow in such a way that the horizontal velocity component is substantially reduced to zero, the vertical velocity component dominating over a vertical distance of which the height is at most equal to the distance over which the horizontalvelocity component dominates. The change in direction is carried out in such a way as to avoid disintegration of the oil stream although the oil layer may during the change in direction be broken into a plurality of separate streams which re-unite at the beginning of the next stage. The most favourable results are attained if during the change of direction the flow of the oil is entirely free from interference from the flow of the lye solution. This can conveniently be done by physically separating the flow of the lye and the oil from each other by causing one or both to pass through pipes or separate compartments so that contact of one with the other is avoided.

The formation of globules of oil where the change of direction occurs is to be avoided since it would reduce the efficiency of the refining process. If globules are formed they do not always coalesce during the rest of the process. It is an important feature of the process according to the invention that such turbulence as would result in interruption of the continuity of the oil stream is avoided.

With this in view the angle of the guiding plates along which the oil gradually flows upwards should preferably be smaller than 20, angles less than 10 being particularly preferred. The use of guiding plates which are horizontally placed and along the underside of which the oil spreads, is not excluded.

As indicated above the alkaline solution may flow countercurrently as well as concurrently with the oil. The choice of the more suitable way depends on practical considerations. In order to obtain a suflicient neutralisation the oil layer should have a thickness of some millimetres. In general good results are obtained when the throughput of the oil is kept below 10 litres per hour per cm width of the oil layer, a suitable throughput being 2 to litres per hour per cm width.

When the process is carried out as described, with due regard to the various precautions referred to above, it is found that during the changes in direction of the oil stream contact between that stream and the aqueous soap layer formed is broken and this is considered an important factor in obtaining the desired results.

The process of the invention is applicable to a great variety of crude oils and even with those having a very high free fatty acid content products have been obtained of free fatty acid content of 0.15% or even less.

The presence of a small proportion of soap in the alkaline solution has been found to facilitate the neutralisation and with this in view soap and/or other wetting agents may be added to the fresh lye. Small proportions of sodium chloride or like electrolytes may also be added. It is of advantage to use sodium hydroxide as the alkali, but other alkaline agents are also applicable. In general an alkaline solution with a concentration of 0.05 to 1.5 N is applied, the range of 0.1 to 0.8 N being preferred.

in general, the oil neutralised as described above is subjected to a further refining treatment including drying, bleaching, deodorising with or without an intermediate hardening step. It is also of advantage to include between the neutralisation and said further refining treatment an additional treatmentt with lye to remove colour and to reduce the free fatty acid content further. This treatment may, for example with a vegetable oil, comprise agitation with a weak lye, e.g. 0.2 N aqueous caustic soda, followed by the separation of the oil and aqueous layers by centrifuging or decantation. With animal fats, especially lowgrade animal fats like tallows, a much higher concentration of lye may be desirable. This additional treatment with aqueous alkali of a concentration ranging from 0.1 N to as much as 4 N-8 N or even higher may be used, according to the nature of the oil treated.

Various arrangements according to the invention are referred to in the Examples that follow and are shown diagrammatically in the accompanying drawings.

FIGURE 1 of the drawings shows in sectional elevation guide means for use in guiding the oil layer upwards along a step wise path.

Referring to the figure, reference numeral 1 represents a long rectangular guide plate having side flanges 2 extending downwards from what will be the under surface 3 of the plate in use. (This surface will be referred to below simply as the under surface.) At intervals substantially rectangular bafiles 4 project downwards at an angle of 2-10 from the under surface 3. These baflles are provided with downwardly projecting side flanges 5.

In operation the guide plate 1 is located at an inclination of 2 to 10 to the horizontal in a duct which is preferably of uniform rectangular cross section the upper wall being adjacent to the plate 1, the lower wall being parallel to the upper wall and spaced apart therefrom sufficiently to allow the desired flow of alkaline solution and oil through the duct, and the side walls being adjacent to the side flanges 2. FIGURE 1 shows the upper wall 6 and lower wall 7 of such a duct.

With such an arrangement the alkaline solution may enter the duct at either end according as it is required to flow counter to or in the same direction as the oil through the duct. The oil enters the duct at the lower end in the vicinity of the lower surface 3 and flows upwards as a layer in contact with that surface until diverted by the first of the baflles 4, along the under surface of which it then flows to the end of the baffle. Thence it rises substantially vertically through the alkaline solution and then in contact with the surface 3 until diverted by the next baflle.

Thus it pursues through the duct, an upward substantially stepwise course in which relatively long gentle generally upward slopes alternate with relatively short substantially vertical rises.

During the flow of the oil through the duct the flanges 2 prevent the oil layer from spreading into any space between these flanges and the side walls of the duct and the flanges 5 serve a similar purpose. The oil at the end of its path is separated from the alkaline solution and from the aqueous soap solution that has been formed in the neutralisation. This separation may be effected when the flow is concurrent by causing the oil to pass over a weir into a collecting vessel from which it flows away while the alkaline and soap solutions are constrained to pass beneath the collecting vessel to a separate outlet. FIGURE 2 shows a suitable arrangement for effecting the separation.

In FIGURE 2, in a housing 8 having an inlet 9 into which flows the alkaline solution and the supernatant oil layer, is located an oil collecting vessel 10 into which the oil flows over a weir 11 and from thence through the outlet 12 while the alkaline solution flows through the passage 13 under the oil collecting vessel and then over a second weir '14 into a compartment 15 provided with an outlet 16.

It has been stated above that the baffles 4 are substantially rectangular but it is advantageous for the battles to taper slightly so that towards the free ends of the baffle the oil layer is constricted in width. Alternatively, with the same object the baflles may be reduced in width by recessing. Also, an arrangement of apertures and obstructions may be provided near the free ends of the batfles to break the oil layer into a number of streams for its upward flow through the alkaline solution. Details of various constructions for the baflles are shown in FIGURES 3 to 6.

FIGURE 3 shows a forwardly tapering baflle 4a having a rear projection 17 by which it is attached to the under side of the guide plate 1 the flange of which is not shown. The opening 18 (between the baflle and its flanges 5), through which the oil layer flows, is unobstructed.

FIGURE 4 shows a forwardly tapering balfle 4b the Opening 18 from which is obstructed by teeth 19 which breaks up the oil layer into separate streams.

FIGURE 5 shows a bafiie 40 which is recessed at 20 and in which in addition to the opening 18 partially obstructed by teeth 19 there are provided side openings 21 partially obstructed by teeth 22.

FIGURE 6 shows a baffle 4d which is recessed at 20 and in which a forward flange 23 serves completely to close the forward flow of the oil, apertures 24 being provided to break the oil film into a number of separate upward flowing streams.

Instead of providing mere apertures as in FIGURE 6 for the passage of the oil in separate streams through the alkaline solution, pipes may be provided for this purpose so that these oil streams are free from interference. Alternatively, or in addition, pipes may be provided through the bafiies for the passage therethrough of the alkaline solution without intereference with the flow of oil. When the flow of alkaline solution through a conduit provided with guide means of the kind specified above is counter to that of the oil, to avoid interruption of the oil stream in its upward substantially vertical flow from the bafiles it is very desirable that the baffles should be provided with some means, such for example as have been described above, for breaking the oil layer into a number of coherent streams.

Instead of a guide plate provided with bafiles a plurality of simple guide plates in series, each located in a separate upwardly inclined conduit, may be used, means being provided for feeding the oil layer emerging from under the plate at the top of one conduit to a region under the plate at the bottom of a succeeding conduit, together with means for feeding the alkaline solution in below the oil layer at the bottom of one conduit, out at the top thereof and thence to the bottom of a preceding conduit so that the flow through each conduit is concurrent while that from one conduit to the next is countercurrent. FIG- URE 7 shows an arrangement of this kind.

In FIGURE 7 reference numerals 25 and 26 indicate two inclined conduits of rectangular cross-section in each of which is axially located a guide plate 27, each conduit communicating at its upper end with means 28 and 29 respectively, of the construction shown in FIGURE 2, for separating oil from alkaline solution. Oil from a storage tank 30 provided with a heater 31 is pumped through the pipe line 32 to the lower end of the conduit 25 in the vicinity of the lower surface of the guide plate 27 by means of a pump 33, passing on its way through the heat exchanger 34 and flowmeter 35. After passing along the lower surface of the guide plate 27 it is separated from the alkaline solution by the separator 28 and is then passed through pipe line 36 on to the lower end of the conduit 26 where the same process as in conduit 25 is repeated. The oil, after being separated from the alkaline solution by means of the separator 29, is then passed by means of the pipe line 36a to a collecting vessel 37, provided with a heater 38. The alkaline solution from a storage tank 39, provided with a heater 40, is pumped through the pipe line 41 to the lower end of the conduit 26 (thus flowing in the same direction as the oil) by means of a pump 42, and after having passed the heat exchanger 34 and a flowmeter 43. After having passed through the conduit 26 and been separated from the oil by means of the separator 29 the alkaline solution flows along a pipe line 44 to a buffer vessel 45 from which it is pumped along pipe line 46 to the lower end of the conduit 25 by means of the pump 47 passing on its way through the heat exchanger '34 and flowmeter 48. After having passed through conduit 25 and been separated from the oil by means of the separator 28 the alkaline solution flows along a pipe line 49 to a collecting vessel 52 provided with a heater 53. Thus whereas the flow of the oil and the alkaline solution in each of the conduits 25 and 26 is concurrent, their general flow is countercurrent, the oil passing first through the conduit 25 and then through the conduit 26, and the alkaline solution passing through said conduits in the reversed sequence.

A more compact arrangement in which the plates are mounted zig-zag is shown in FIGURE 8, which shows in cross-section two of such plates. In a casing 54 of rectangular cross-section are mounted the guide plates 55 and 56. At the upper end of each guide plate downward flanges 57 and 58 serve to close completely the forward flow of the oil, and near the upper end of each guide plate apertures 59 and 60 are provided to break the oil film into a number of separate upward flowing streams. Between the flanges 57 and 58 and the wall of the casing, openings 61 and '62 are provided to allow the alkaline solution to flow without disturbing the oil flow.

Instead of providing mere apertures (as in FIGURE 8) for the passage of the oil in separate streams through the alkaline solution, pipes may be provided for the purpose so that these oil streams are free from interference.

Another alternative is shown in FIGURE 9. Here, again, a number of guide plates are mounted in zig-zag arrangement in a casing 63 of rectangular cross-section, two of these guide plates 64 and 65 being shown. Pipes 66 and 67 are provided, extending downward through the guide plates 64 and 65 beyond the lower limit of the oil layer to allow the alkaline solution to pass separate from the oil. This allows the oil to move upwards as a layer, instead of as separate streams, through the openings 68 and 69 between the Wall of the casing and the flanges 70 and 71 at the upper end of the guide plates 64 and 65, the said flanges being provided to prevent any disturbance of the oil layer by suction of the alkaline solution passing through pipes 66 and 67. This arrangement has been found to be extremely effective.

The total number of guide plates in the arrangements shown in FIGURES 8 and 9 will depend on the type of oil to be treated and the final free fatty acid content desired and, of course, also on the dimensions of the guide plates used.

Instead of guide plates of the type shown in the drawings, helical or part conical guide plates may be used. Moreover, horizontally mounted guide plates may be used, the flow of oil then being caused by the introduction of oil at one end of the guide plate and the upward escape of oil at the far end of said guide plate, which is provided with flanges to prevent the oil from escaping under the guide plate at the introduction stage or along the sides of the guide plate.

When using a number of guide plates these guide plates are usually identical but a sequence of guide plates of different types is also effective. Thus, when an oil with a high content of free fatty acid (5% by weight ofthe oil or more) has to be refined, it may be advantageous to use, for example, a combination of a long horizontal or sloped guide plate as the first stage and an apparatus as shown in FIGURES 8 and 9 as the following stage.

FIGURES 10, 11 and 12 show a form of construction in which horizontal guide plates are mounted in a cylindrical vessel. FIGURE 10 is a schematic diagram in side elevation showing an arrangement of the plates Within the vessel, FIGURE 11 is a plan view of a plate having fewer holes than those shown in FIGURE 10 and FIGURE 12 is a cross section along the line AA in FIGURE 11.

Referring to FIGURE 10, within a cylindrical vessel 72 are located a number of circular plates 73 of identical construction and separated by distance pieces 74 threaded on rods 75 passing through holes 75a in the plates, and sealed at the Walls of the vessel by rubber rings 76. Each plate is provided with a number of circular holes 77 and 78 of which 77 are larger than 78 the distance d (see FIGURE 11) between each hole of a particular size and the nearest hole of the same size being constant. The holes are so arranged that if two plates are superimposed with corresponding holes registering, then on rotating one plate through relative to the other in one direction,

the small holes in the upper plate will register with large holes in the lower plate but no small hole in the lower plate will register with a hole in the upper plate.

A suitable arrangement of holes can be obtained by a construction in which a grid of equilateral triangles with side d is superimposed on the plate with one line XY of the grid passing through the centre thereof with the nearest apex P at a distance of d/ 3 from that centre. Each apex of the grid marks the centre of one small hole. This grid is then rotated by 60 above the centre of the plate. Each apex then marks the centre of a large hole. The construction described may if continued far enough towards the edge of the plate produce an excess of one size of hole over the other, as in FIGURE 11 which shows 16 large holes and 18 small. This is to be avoided and in constructing the plate shown diagrammatically in FIGURE 11, the two small holes furthest from the centre are omitted.

The plates are flanged round the edges of each hole to form a funnel or spout with the hole at the centre. (The flanging is conveniently effected in punching the hole in the plate.) The spouts 79 of the large holes 77 project upwards while the spouts 80 of the small holes 78 (which provide passages for the downward flow of lye through the apparatus) project downwards into the large holes 77 leaving annular spaces 81 for the upward flow of oil through the apparatus.

Above the uppermost of the plates 73 and separated therefrom by an oil-collecting space 82 is a cover plate 83. The vessel has an outer cover 84 having a lye inlet pipe 85 communicating with a space 86 above the plate 83. An oil outlet pipe 87 passes through the cover 84 into the oil-collecting space 82. From the space 86 lye distributing pipes 88 project downwards through the oilcollecting space and the holes 77 of the uppermost of the plates 73. Below the lowest of the plates 73 is a spent-lye collecting space 89 having an outlet pipe 90 for the spent lye. Oil inlet pipes 91 project into the upper part of this space in positions that are not immediately below any of the holes in this plate.

In operation, lye is admitted continuously through the inlet pipe 85, fills the space 86 and flows downwards through the pipes 88 and thence over the surface of the second of the plates 73, through the spouts 80, over the surface of the next plate and through the spouts 80 thereof and so on as indicated by the downward arrows, to the spent lye collecting space 89 and out through the outlet pipe 90. Meanwhile, oil fed continuously through the inlet pipes 91 flows along the underside of the lowest of the plates 73 and up through the annular spaces 81 and thence along the lower surface of the next plate and up through the annular spaces 81, and so on, as indicated by the upward arrows, to the oil-containing space 82 from whence it is drawn off through the oil outlet 87.

During the passage of the oil counter to the flow of lye neutralisation of free acid in the oil progressively occurs with an efficiency that depends on the renewal of the surface of contact between the phases that constantly occurs as the result of the passage of the oil through the annular spaces.

The following examples illustrate the invention.

Example 1 The apparatus was as shown in FIGURE 7 of the drawings. Each guide plate was of length 3.5 m. and width cm. and downwardly projecting flanges 1 cm. in depth.

Two series of trials were carried out, one with the conduits (and their guide plates) inclined at 7 to the horizontal and one at 10.

The oil treated was unrefined coconut oil containing 3.9% of free fatty acid.

The alkaline solution was a 0.4 N aqueous solution of sodium hydroxide. The temperature in the conduits was kept at about 90 C.

The results ars shown in Table I. In the table the throughputs of oil and alkaline solution are expressed in terms of litres per cm. width of guide plate per hour. Percentages of free fatty acid (f.f.a.) and of soap are based on weight of refined oil obtained.

The process was carried out as in Example 1 except that a large part of the alkaline solution emerging from the upper conduit was recirculated after the addition of a small proportion of fresh alkali. This was effected by increasing the flow of alkaline solution to eight times its value in Example 1, continuously adding to the circulating alkaline solution one seventh of its volume of fresh alkaline solution on the inlet side of the apparatus and continuously withdrawing an equal volume of alkaline solution on the outlet side.

The results are shown in Table II, where column 2 shows the throughput of fresh lye.

Example 3 The appartus was as shown in FIGURE 1 except that the baflies 4 were of the construction shown in FIGURE 5, the guide plate being 4 crns. wide and crns. long and inclined to the horizontal at an angle of 7, the baffles (33 in number) being horizontal, and the guide plate being mounted in a glass tube of internal diameter of 5 crns. The oil and alkaline solution were passed through the tube in the same direction at speeds of 2 and 1.2 litres per cm. per hour and the jets of oil had an upwards path of about 1.5 crns. in passing from one bafile to the next.

The oil treated was coconut oil of free fatty acid content 3.8%. The alkaline solution of 0.4 N sodium hydroxide. The free fatty acid of the refined product was 0.2 to 0.3%.

Example 4 The refined oil from Example 3 was subjected to a further refining treatment identical with that of Example 3 and this reduced the free fatty acid content to approximately 0.07%

In Examples 3 and 4 the baffles described can be replaced by baffies of the construction shown in FIGURES 4 or 6. With plain baflles as shown in FIGURE 3 the reduction in free fatty acid content was less and there was a greater tendency to emulsification resulting in greater loss of oil.

The efiiciency in these examples could obviously be increased by replacing the circular tube with a conduit of rectangular cross section in which the guide plate is located in close juxtaposition to the upper wall so as to avoid dead space above the plate.

Example 5 The apparatus was composed of two units in series. The first was a conduit of rectangular cross section, of width 10 crns. and length 350 crns., provided with a simple rectangular flanged guide plate parallel with the axis of the conduit, and contiguous to its upper wall, the plate and conduit being inclined at 10 to the horizontal.

The second unit was a tower containing 22 plates, in zig-zag arrangement as shown in FIGURE 8; each plate having near its upper end 10 holes (59, 60) each 0.2 cm. in diameter, and the slope of the plates being 9 to 10.

These units were connected so that the oil flowed first upwards through the conduit then upwards through the tower (being guided by the lower surface of each plate in turn and passing from plate to plate through the holes 59 and 60) while the alkali flowed (beneath the layer of oil) first upwards through the conduit and then upwards through the tower.

The product had a free fatty acid content 0.02 to 0.07%. The refining factor estimated as:

weight of crude oilweight of refined oil weight of free-weight of free fatty acid in fatty acid in crude oil refined oil was only 1.3. The percentage of soap in the refined oil was only 0.02 to 0.04.

Example 6 The apparatus was as described in Example except that the conduit and its guide plate were 200 cms. long and 5 cms. wide and the tower was provided with 34 guide plates arranged zig-zag, the slope of the plates being 3 to 4 and short pipes being provided, corresponding to each hole in the plates, for carrying the oil streams through the alkaline solution from one plate to the next. The distance between the upper ends of these pipes and the lower surface of the next plate was about 0.4 cm.

The oil treated was and the alkaline solutions were as specified in Example 5, and the direction of flow of oil and alkaline solution were as described in that example, the rate of flow being 11 to 14 litres per hour for the oil and 14 litres per hour for the alkaline solution.

The refined oil had a free fatty acid content of 0.06 to 0.09%, the soap content of the refined oil was 0.01% and the refining factor was 1.2 to 1.3.

Example 7 The refining was effected in a tower provided with guide plates in zig-zag arrangement as described in relation to FIGURE 9, there being 50 plates each of length 17 cms. and width 5 cms. each plate having a hole 0.8 cm. in diameter near its upper end, each hole being provided with a short pipe to carry the alkaline solution downwards through the oil layer onto the plate below, The upward projecting flanges 70 and 71 at the end of each plate were of height 0.4 cm.

The oil treated was coconut oil of free fatty acid content 4.4%. The alkaline solution was 0.4 N sodium hydroxide. The oil was fed into the tower immediately below the lowest plate at a rate of 15 litres per hour and flowed upwards guided by the lower surface of each plate in turn and at the upper end of each plate flowing upwards through a gap (68 or 69) to the next plate.

The alkaline solution was fed into the space above the top plate at the upper end thereof at a rate of 15 litres per hour and flowed downward in contact with the upper surface of each plate in turn passing from one plate to the one below through the pipes 66 or 67.

The product was of free fatty acid content 0.08 to 0.14% and soap content 0.01% and the refining factor was 1.2.

Example 8 The process was carried out as in Example 7 but using as the alkaline solution 0.2 N sodium hydroxide. The product was of free fatty acid content 0.14 to 0.17%, soap content 0.01% and the refining factor was 1.12.

Example 9 The process was carried out as in Example 7 but using as the alkaline solution 0.8 N sodium hydroxide. The product was of free fatty acid content 0.09 to 0.13%, the soap content was 0.01% and the refining factor was 1.19.

Example 10 The process was carried out as in Example 7 but using as the alkaline solution 0.2 N sodium hydroxide. The product was of free fatty acid content 0.18% and a soap content of less than 0.01%

The product was collected in a vessel into which an alkaline solution of 0.2 N sodium hydroxide was continuously fed at the rate of 4 litres per hour. The vessel was provided with a single-bladed stirrer which rotated at about 100 rpm.

The mixture of oil and alkali was centrifuged in a centrifuge of the hollow bowl type, which rotated at about 30,000 rpm. The housing of the centrifuge was heated to about C. The diameter of the separation cylinder in the centrifuge was 40 mms. The free fatty acid content in the so treated oil was 0.01%. The refining factor was estimated at 1.14.

Example 11 The refining was effected in a tower provided with guide plates in zig-zag arrangement as described in relation to FIGURE 9, there being 40 plates each of 17 cms. length and width 10 cms., each plate having two holes each 0.9 cm. in diameter near its upper end, each hole being provided with a short pipe to carry the alkaline solution downwards through the oil layer onto the plate below, the slope of the plates being 5. The upward projecting flanges 70 and 71 at the end of each plate were of height 0.6 cm. and ended 0.17 cm. below the next upper plate. The oil treated was lowgrade tallow with different contents of free fatty acid. The oil was treated in concurrent as well as countercurrent with the alkaline solution, using different alkaline concentrations and different throughputs.

The results are given in Table III.

TABLE III Oil Percent Lye throughput t.i.a. Trial Percent concenin m. /h./m. refined No. t.f.a tration width oil Lye/oil flow 0.1 N 0.20 0. 24 countercurrent. 0. 2 N 0. 30 0. 28 Do. 0. 2 N 0.30 0.36 Concurrent. 0. 1 N 0. 20 0. o. 0. 1 N 0. 20 0.58 Countercurrent.

Example 12 Lowgrade tallow was subjected to a refining treatment in an apparatus composed of two units in series.

The first was a conduit of rectangular cross-section of width 10 cms. and length 200 cms., provided with a simple rectangular flanged guide plate parallel with the axis of the conduit, and contiguous to its upper wall, the plate and conduit being inclined at 10 to the horizontal.

The second unit was a tower as described in Example 11. The oil flowed first upwards through the conduit and then, after being flown over a weir, was pumped into the tower. In the tower fresh alkali flowed either in concurrent or in countercurrent to the oil.

The results are shown in Table IV.

TAB LE IV Oil Percent Alkali throughput Lila.

lowgrade tallow having a free fatty acid content of 5.02%. The product had a free fatty acid content of 0.40% and a soap content of 0.01%

The product was collected in a vessel with stirrer, and a concentrated alkali solution of 4 N was added. After 11 3 minutes stirring hot Water was added in such an amount that the theoretical concentration of the alkali was estimated at 0.2 N. The mixture was heated and kept at 90 C. and after minutes stirring the soap was decanted.

The free fatty acid content of the oil was 0.02%.

Example 14 In an apparatus of the construction shown in FIGURES 10 to 12 coconut oil was refined.

The cylindrical vessel 72 was of diameter 500 mms. and height 390 mms. Within the vessel twenty-two horizontal plates 73 were provided which were kept in place by seven rods 75 mounted in the bottom of the vessel. The plates were kept at a distance of 10 mms. from each other by means of distance pieces 74. In each plate were sixteen perforations 77 with a diameter of 32 mms. each having an upwardly inclined flange forming a spout 79, and sixteen perforations 78 of diameter 11.5 mms. each with a downwardly directed flange forming a spout 80. The holes were arranged according to the pattern shown in FIGURE 11. During mounting each plate was rotated 120 in relation to the one below so that the spouts of the small perforations of one plate projected into the large perforations of the plate below. Thus a path was provided by the annular spaces 81 between the spouts of the small holes and the edges of the large holes into which they projected. The length of path could be varied by changing the vertical spacing between plates by changing the thickness of the distance pieces. The upper and lower plates were provided with sixteen small inlet pipes 88 for the lye and sixteen small inlet pipes 91 for the oil. In the cover 84 of the apparatus the main lye inlet 85 as well as the oil outlet -87 were provided, and in the bottom plate (unnumbered) was provided the outlet 90 for spent lye.

The vessel was first charged with lye which filled the space between the plates. Then oil was introduced at the bottom and flowed along the underside of the plates upwards through the annular spaces 81 into the oil collecting space 82. Lye was continually fed into the system through the inlet 85 and oil through the inlets 91, refined oil being removed through outlet 87 and spent lye through outlet 90.

Crude coconut oil with a free fatty acid content of 4.67% and a moisture content of 0.17% was reflned by treatment in the apparatus with 0.1 N lye. The velocity of the oil was 100 litres per hour and about 109.5 kg. of oil were treated. The free fatty acid content of the refined oil was 0.29, the soap content was 0.115. The refining factor was estimated at 1.02.

The invention has been described with particular reference to the refining of coconut oil. In the same way a variety of other glyceride oils can be refined, including for example, palm oil, palm kernel oil, groundnut oil, cottonseed oil, soyabean oil, rapeseed oil, sunflower oil and safflower oil, as well as animal and marine oils, for instance lard, tallows, whale oil and fish oils, whether hardened or unhardened. The process must of course be carried out at a temperature at which the oil treated is sufficiently mobile to flow readily through the apparatus. Temperatures of 70 or 80 to over 90 C. are generally advantageous and specially good results have been obtained at even higher temperatures, for instance 95 to 100 C.

The invention includes apparatus suitable for carrying out the process of the invention. Such apparatus may include means for constraining a stream of alkaline solution to flow along a predetermined path in which any inclination to the horizontal is small, inlet means for said solution at one end of said path, outlet means for said solution at the other end of said path, inlet means for introducing the oil above the level of said solution at an end of said path that is not higher than the other end, and guide means for guiding the oil layer in succession along each of a series of paths in which any inclination to the horizontal is upwards at a small angle thereto, the said guiding means being so constructed and arranged that between consecutive paths of said series contact of the oil with any layer of aqueous soap solution that has been formed is broken without substantial intermixture of the oil with the alkaline solution or the soap solution.

In general terms apparatus according to the invention comprises a system of conduits for carrying oil and aqueous alkali, an inlet for aqueous alkali at one end of said system and an outlet therefor at the other end, an oil inlet at one end of said system and an outlet therefor at the other end, within said system a plurality of guide members each having a guide surface above and extending along one of a series of spaced apart flights forming parts of a circuitous path for oil and aqueous alkali, each flowing from its respective inlet to its respective outlet, the oil along most of the path flowing on the surface of the aqueous layer, any inclination of said flights to the horizontal being upwards in the direction of oil flow at an angle not greater than about 10 and means situated between the forward end in said direction of each such flight and the rear end of the next of such flights for disrupting the interface between the aqueous and oil layers and causing oil and alkaline solution to pass in separate coherent streams from said flight to the next.

As indicated above with reference to the drawings one suitable arrangement comprises an inclined conduit in which is located a guide plate for the oil layer having bafiles arranged to provide the separate paths of the series referred to, holes or pipes near the end, or teeth at the end, of the bafiles serving to break the oil layer and alkaline solution into separate streams, the oil flowing steeply upwards from one path to the next in the form of coherent streams so that substantial intermixture with the alkaline solution or soap solution is avoided.

Or as indicated with reference to FIGURE 7, a plurality of separate inclined conduits each with its guide plate can be provided, the oil layer at the top of one conduit being separated from the alkaline solution and soap layer and carried by a separate pipe line to the bottom of the next conduit.

Or as described with reference to FIGURES 8 and 9, a zigzag arrangement of plates can be provided with a substantial vertical gap between the top of one and the bottom of the next, suitable means being provided for causing the desired separation of oil from aqueous media without substantial intermixture. For instance, such means may comprise, as shown in FIGURE 8, holes (or pipes) near the upper ends of the plates to canalise the oil into separate vertical streams flowing through the aqueous media without intermixture and a gap between the downwardly projecting end flange at the upper end of each plate to accommodate the flow of aqueous medium. Alternatively, as shown in FIGURE 9, pipes may be provided to break the alkaline solution into streams passing through the oil layer without contact therewith while the oil layer flows vertically upwards through a gap between the upwardly projecting end flange at the upper end of the plate and the casing into contact with the next plate.

In general apparatus of the kind shown in FIGURES 10 to 12 is preferred since in such apparatus economy of space can be combined with high efliciency.

What is claimed is:

1. A continuous process for the alkali refining of a glyceride oil by contact with an aqueous alkaline solution, comprising the steps of bringing the oil, in the form of a thin, coherent supernatant layer, into contact with a stream of alkaline solution flowing counter or concurrent thereto in each of a succession of treating stages at an inclination of 0 to about 20, to form an aqueous soap layer at the interface, transferring the oil and aqueous phases between consecutive treating stages, disrupting between consecutive stages the aqueous soap layer formed at the interface and exposing the oil layer to a surface of the aqueous layer bearing less soap, and separating the 13 oil from the aqueous phase at the end of at least the last of the said stages.

2. A continuous process for the alkali refining of a glyceride oil by contact with an aqueous alkaline solution, comprising the steps of bringing the oil in the form of a thin, coherent supernatant layer into contact with a stream of alkaline solution flowing counter or concurrent thereto in each of a succession of consecutively elevated treating stages at an inclination of to about 20 to form an aqueous soap layer at the interface and releasing the oil layer at the end of each stage to float upwardly into the next succeeding stage in a more steeply inclined path to disrupt the aqueous soap layer at the interface between the aqueous and oil layers while maintaining the co herent entity of the oil layer, thereby dispersing the soap concentrated at the interface into the aqueous phase, and separating the oil and aqueous layers at the end of at least the final treating stage.

3. Process according to claim 1 wherein the aqueous soap layer is disrupted between consecutive stages by physically separating the aqueous soap layer from the oil layer.

4. Process according to claim 2 wherein the soap layer is disrupted by constricting the width of the oil layer adtween each pair of consecutive stages follows a path in which its horizontal velocity component is substantially zero.

6. Process according to claim 5 wherein the oil flows substantially vertically between consecutive stages for a distance not more than that of each stage.

7. Process according to claim 2 wherein the oil layer flows in a zig-zag direction counter-current to the aqueous layer and floats upwardly through the falling alkali stream in at least one coherent stream between consecutive stages.

8. Process according to claim 1 wherein the throughput of the alkali stream is 2-5 litres per centimeter of thickness of the oil layer per hour and the concentration of the alkali is from 0.1 N to 8 N.

References Cited UNITED STATES PATENTS 2,906,606 9/1959 Signer 23-270.5 3,226,407 12/ 1965 Bergman 260425 ALEX MAZEL, Primary Examiner.

A. M. TIGHE, Assistant Examiner.

US. Cl X.R. 

